Carbon fiber polymer composites have attracted worldwide interest in sporting goods and aerospace industries due to their excellent specific strength, stiffness and lightweight. Thus the synthesis, structural characterization, and cyclization studies of polyacrylonitrile (PAN) based precursors have received a great deal of attention in recent years. PAN-based carbon fibers are usually produced by the following steps: 1) spinning of precursors; 2) oxidative stabilization and carbonization of fiber precursors. Solution spinning of the precursors is carried out at different drawing rates while stabilization typically occurs around 200-300° C. in air, which leads to the formation of a ladder polymer necessary to obtain a high quality carbon fiber. The step of forming ladder polymers is very important, as it influences the physical properties and the microstructure of the resultant carbon fibers. Subsequently, carbonization is carried out at temperature of 1000-1400° C. in an inert atmosphere which removes nearly all of the non-carbon elements. The resulting carbon fibers are used to produce the reinforced polymer composites which are known to give high strength, high modulus, light weight and high heat resistance.
PAN-based carbon fiber precursors are preferred reinforcement for structural composites in various aerospace and military applications and have attracted worldwide interest in their use for sporting goods to aerospace industry due to their excellent specific strength and stiffness combined with their lightweight. The traditional carbon fiber precursors degrade before they melt therefore, the precursor fibers are generally solution-spun (20-30 wt % solution) in polar solvents. The solution spinning involves the disadvantages of solvent toxicity, solvent recovery and higher processing cost which restrict their use to limited number of applications necessitating to prepare the cost effective carbon fibers to expand their applications in other sectors like sports and automobile industries. Melt processable carbon fiber precursors based upon the terpolymer of acrylonitrile, methyl acrylate and acryloyl benzophenone (ABP) are known, which require UV stabilization which again leads to higher cost.
There is therefore a need to develop melt processable carbon fiber precursors at a lower cost. The claimed invention provides a method for forming a carbon fiber precursor by melt spinning, which can be thermally cross-linked in air.